Tomorrow morning, Apple shares are going to get clobbered following the news that CEO Steve Jobs is taking a third medical leave. Several aspects of the announcements are bothering the Street. One, he's making no promise this time on when he might come back - last time, Apple said he'd be out six months, and that's how long he was gone. And two, there's something sad and worrisome about his comment that "I ... hope to be back as soon as I can," which implies, well, maybe he won't be back so soon, or maybe at all.

With the stock market shut down today for the Martin Luther King holiday, the reaction from the analyst community has been fairly limited so far, but you can be sure that there will be a burst of commentary tomorrow morning, and another round Wednesday morning after the company reports December quarter results after the close on Tuesday.

My discussions with analysts so far suggest fairly widespread concern that this time, Steve might not be coming back - that his health problems simply aren't consistent with someone dealing with the pressures of running a company pushing $100 billion in annual revenues. And there also is some anticipation that for anyone who has been waiting for a chance to buy the stock, tomorrow morning's anticipated sell off could provide the perfect entry point.

Gleacher & Co. analyst Brian Marshall said in an interview that he thinks the stock tomorrow could test the $300 level - which would be a drop of around 15%, knocking $50 billion in market cap from the company's valuation. At that, point, he said, the stock would basically be trading at 12x his forecast of $22-$23 a share in profits for calendar 2011, given the company has about $55 a share in cash - and would offer a good entry point for investors. Marshall's assessment is that there is no better than a 50/50 chance that he comes back this time as a full-time CEO. "My belief is that this is the last time we'll probably see Steve as CEO," he says. "I expect Tim Cook to be named CEO sometime this year."

Gene Munster, an analyst at Piper Jaffray, says that despite the wording of the release, investors fear there is something more serious happening this time. Munster says he's always thought that the stock would take a 10% hit in a post-Steve world - and in European trading, the shares are trading down 6%-8%. He's expecting a 5% fall in U.S. trading tomorrow. In short, investors are treating the stock as if Jobs already has stepped down from the top job.

In an interview, Munster notes that from a day-to-day management perspective, replacing Jobs with Cook as CEO would change nothing; he notes that Cook has effectively been running Apple since Jobs returned from exile in 1997. Munster thinks there would be little immediate impact on the Apple org chart from such a change, although he notes that key players would gain in stature inside the company, including product design guru Jonathan Ive. The real issue will be that "Jobs is irreplaceable...his product inspiration, no one can touch that."

On the other hand, he also notes that "we've been through this before, and historically, it has been a buying opportunity." The company's game plan for the next 1-2 years is already in motion. If the stock really does open down 10% or more tomorrow, he says, it will be a buying opportunity. The longer term question, he says, is how the possibility of Apple without Jobs will affect the P/E multiple investors are willing to pay for the stock. Munster notes that there is an "optionality, wild-card potential" to Apple with Steve at the helm, the idea that he might launch the company into a giant new market at any particular moment, that is factored into the stock.

As for tomorrow afternoon's earnings report, Munster says the message is likely to be that "things are going great." He expects a lot of good financial news. And he says the bottom line message will be that Apple is "effectively taking over the technology world," as it spreads its wares from the developed market into emerging economies. "Whether the stock is up or down on Wednesday [after earnings and the Jobs news] is in some ways irrelevant," he says. "What is more important is the broader theme, which is that they are taking over the world." Even if Steve is cheering Apple on from the sidelines.